Well, even if the worst happened and the AMA leaves, I think they'd relocate to a new location, and maybe one that's every bit as interesting as the Lane house. I recall when they had the Variety Arts Theater in a very cool, historic building downtown. Something like that could be a successful "Castle." And don't the Larsens own most of the interior furnishings? They can strip the place. So the bookcase will still admit, Irma will still play, Houdini will still haunt the Seance Room, and once the doors to the showrooms are closed, you'll feel as if you're in the same old "Castle". Yes, it would be sad day for magical tradition and a flat-out tragedy for Hollywood to lose such an historic landmark, but the AMA would go on.
Also, the Glovers and any potential tenets should realize that 1000 sorcerers will lay 1000 curses on that property, so...food for thought. :p